Unit 2 - Week 2 - Shillitoe, Stein 4 and 5, and Hanes Flashcards
How many genes do parvoviruses have? What are there functions?
2 genes: replicative and capsid
How many genes do retroviruses have?
About 3 genes
How many genes do papillomaviruses have?
About 8 genes
How many genes do adenoviruses have?
About 10 genes
How many genes do herpesviruses have?
70+ genes
Are viral genes prokaryotic or eukaryotic?
Eukaryotic
Gene expression is regulated by _____ TF’s. For example, papillomavirus gene expression is regulated by keratinocyte proteins, and Hebatits B virus gene expression is regulated by liver proteins.
Cellular
Give an example of viral genome efficiency.
The reading frames for genes can overlap on the same strand and/or on complementary strands.
What percentage of the viral genome encodes for tRNA or protein?
100%
True or False: Viruses engage in alternative splicing of RNA.
True
When a virus creates a polyprotein, what is necessary to cleave it into individual proteins, and is therefore the target of antiviral drugs?
Viral protease, especially important with HIV or Hepatitis C
Give three reasons for the high mutation frequency of viruses:
- No proofreading/error correction
- High error rate of viral polymerase/RDRP
- Lake of second strand in some viruses
What are the four types of virus interactions?
- Complementation
- Phenotypic mixing
- Recombination
- Reassortment
What is viral complementation?
If two viruses meet, and one of them is defective at making Y, but the other makes Y, the defective virus can benefit. .
What is viral phenotypic mixing?
If two viruses inhabit the same host cell, some of their capsid/coat proteins or phenotypic expression may be shared, but the genomes will remain parentally unique.
True or False: In viral recombination of homologous viruses, progeny are different from their parents.
True
Most cells or organisms are only infected with one virus at a time because of:
- Competition for resources
- Blocking of receptors
- Stimulation of innate immunity
Name some monogenic disorders that might be treated by viral gene therapy?
- CF
- Retinal disorders
- Immune disorders
- Liver enzyme deficiencies
- Hemophilia
What are some major drawbacks to viral gene therapy?
The amount of virus needed to effect a change is 10^10+++
The effects wear off within about 100 days or so.
Independent survival or an organism requires how many genes?
At least around 500. Pox is one of the bigger viruses and has about 200.
As with bacteria or humans, viral genes comprise:
Enhancer/promoter
Ribosomal entry site
Open reading frame
True or False: DNA and RNA viruses are equally unstable.
False. DNA viruses are stable, about 1 mutation per several hundred to thousand generations, whereas RNA viruses are unstable, about 1 mutation per generation.
Fun fact!
Host range mutations of measles virus allow it to grow in animal cells and to be harvested for use as a live vaccine. The mutation prevents it from growing in the human vaccine recipient.
______ of influenza viruses make previous vaccines obsolete.
Antigenic drift
Name some drug-resistant mutants that have appeared in response to antiviral drugs.
- Acyclovir-resistant mutants of herpes simplex virus
- Protease-inhibitor-resistant mutants of HIV or HCV
- Amantadine-resistance of mutant influenza viruses
Give an example of viral complementation.
Hepatitis D virus cannot grow without Hepatitis B previousl infection because Hep B expresses a surface protein needed by Hep D.
What is a viral pseudotype?
In host cells with more than one virus, sometimes the genome of one virus can get packaged into the capsid of another.
Humans have __1__ polymerase genes while bacteria have only __2__.
- Three (RNA Pol I, II, III)
2. One
Malignancy is uncontrolled cell growth, often accompanies by significant changes in the __1__ of the cells as the chromosomes change over time. Chromosomes are also useful in establishing __2__.
- karyotype
2. clonality
In a metastasis, cells become invaseive and migrate to another site. When the move, they retain:
Their original cell morphology
What is a sarcoma?
Cancer of mesenchymal tissue, like bone, fat, cartilage, muscle
What is carcinoma?
Cancer of epitheloid tissue
What is hepatopoietic/lymphoid cancer?
Leukemias (WBC from bone marrow) and lymphomas (WBC from spleen and lymph nodes)
What is CIN?
Chromosome instability, the gain, loss or rearrangement of chromosomes
What is an oncogene?
A dominantly acting gene involved in unregulated cell growth and proliferation
Most oncogenes are carried by:
Viruses, which carry them, ie H-ras, rat sarcoma virus
sis - Simian sarcoma virus
abl - Abelson murine leukemia virus
Name come viral oncogenes in humans:
HPV (E6, E7) EBV - nasopharyngeal cancer, Hodgkin and Burkitt lymphoma HHV 8 - Kaposi sarcoma HTLV-1 - T cell leukemia HTLV-2 - various leukemias
If an oncogene is not transmitted by a virus, what is the alternative way it can take over in a host cell?
It converted from a proto-oncogene to a oncogene.
What is a proto-oncogene? Give some examples.
A proto-oncogene is a critically important "housekeeping" gene, many are present throughout the human genome: Growth factors Cell surface receptors Regulation of cell cycle DNA binding proteins Intracellular signal transduction
How many mutations in proto-oncogenes are required to cause tumorigenesis? What kind of mutation is this?
Only 1 mutation is needed (dominant), this is a gain of fx mutation
The Philadelphia chromosome refers to the genetic marker associated with what cancer?
CML, chronic myelogenous leukemia
Explain the chromosomal translocation involved in CML.
This is a translocation that occurs between chromosomes 9 and 22, which results in the fusion of a proto-oncogene with a second gene giving rise to a chimeric protein. The result is the loss of properly regulated controls and an overproduction of tyrosine kinase (involved in cell cycle regulation).
The drug Gleevec illustrated the first time:
A medication for cancer was developed based on knowledge of the gene mutation and the resultant aberrant protein. In this way, the side effects can be limited because the therapy is targeted.
What is APL?
Acute promyelocytic leukemia, a dual fusion 15;17 translocation that breaks the PML gene on 15 and the RARA gene on 17.
The fusion signal created by the t(15;17) of APL can be detected using:
FISH
What is a tumor suppressor?
A genetic element whose loss or inactivation allows the cell to display an alternate phenotype leading to neoplastic growth. Mutation requires both alleles (recessive)
What are the 2 types of tumor suppressor genes?
(1) Gate keepers - suppress tumors by regulating cell cycle or growth inhibition
(2) Caretakers - repair DNA damage, maintain genomic integrity
Caretaker tumor suppressors hava a more _____ effect because their loss of fx may not be directly related to disease.
Indirect
Name some normal functions of tumor suppressor genes?
Cell to cell interactions Regulation of growth inhibitory substances Cell proliferation Cell differentiation Chromosome repair
What is MTS1?
Multiple tumor suppressor-1, the second most common tm after p53.
Tumor suppressors are ______, in other words, they only cause disease in one or a few cell types.
tissue specific
True or False: Benign tumors will not have chromosome abnormalities like malignant tumors do.
False! Benign tumors make have karyotypic changes, while malignant tumors may or may not as well.
Rb1 is the ___1___ mutation and functions as a mitotic checkpoint between ___2___ and ___3___.
- classic gatekeeper
- G1
- S
Rb1 is found on chromosome:
13q14.2